1. Digestive System

2. The Digestive System At this station, you will: Compare mechanical and chemical digestion. Learn the parts of the digestive system. Identify the main functions of the digestive system

3. Mechanical vs. Chemical Digestion The process by which your body breaks down food into small nutrient molecules is called digestion. There are two kinds of digestion—mechanical and chemical. In mechanical digestion, foods are physically broken down into smaller pieces. Mechanical digestion occurs when you bite into a sandwich and chew it into small pieces. In chemical digestion, chemicals produced by the body break foods into their smaller chemical building blocks. For example, the starch in bread is broken down into individual sugar molecules.

4. What do you think? Where do you think most mechanical digestion occurs? You might be surprised!!! Where do you think most chemical digestion occurs?

5. Mechanical vs. Chemical cont. Most mechanical digestion occurs in the stomach, not in the mouth. Three strong layers of smooth muscle in the stomach contract to produce a churning motion. This action mixes the food with fluids in somewhat the same way that clothes and soapy water are mixed in a washing machine. Almost all chemical digestion and absorption of nutrients takes place in the small intestine. As the liquefied food moves into the small intestine, it mixes with enzymes and secretions that are produced by the small intestine, the liver, and the pancreas breaking down the food chemically.

6. Functions of the digestive system The digestive system has three main functions. –First, it breaks down food into molecules the body can use. –Then, the molecules are absorbed into the blood and carried throughout the body. –Finally, wastes are eliminated from the body.

7. Parts of the digestive system Food travels through a series of organs as it gets broken down into nutrients the body can use. Peristalsis is the involuntary waves of muscle contraction that keep food moving along in one direction through the digestive system. Food passes through the mouth, esophagus, stomach, small intestine, large intestine (also known as the colon), and rectum before waste is eliminated from the body. Other organs, such as the liver, pancreas, and gallbladder, are known as helper organs. Food does not pass through them but they provide enzymes (chemicals that help food break down) to the main organs to aid digestion.

8. Absorption of the Nutrients Villi – tiny finger-shaped structures that line the small intestine and absorb nutrients. Think about it: Why is important that the small intestine is lined with villi instead of being smooth? Complete the following investigation.

9. Investigation: Importance of Villi Using the model, measure the base of the model as shown in the picture. Use centimeters. Record the total on your paper under smooth surface.

10. Importance of Villi cont. Now measure the villi in the model as shown in the picture. Use centimeters. Record the total on your paper under villi.

11. Importance of Villi cont. Compare the two measurements. Think about it: How do the villi affect the amount of surface area of the small intestine? Record on your paper. Think about it: How do the villi help the small intestine with absorption of nutrients? Record on your paper.

12. Additional Links and Information If you have time, check out these other links and websites. –http://yucky.discovery.com/noflash/body/pg00 0126.htmlhttp://yucky.discovery.com/noflash/body/pg00 0126.html –http://kidshealth.org/kid/htbw/digestive_syste m.htmlhttp://kidshealth.org/kid/htbw/digestive_syste m.html –http://www.childrenfirst.nhs.uk/kids/health/bod y_tour/digestive_system.htmlhttp://www.childrenfirst.nhs.uk/kids/health/bod y_tour/digestive_system.html